New HomePlease visit us at our new home. All content has been moved there.

What is a Kilowatt Hour

The power company charges you for power in kilowatt hours, abbreviated kWh. This guide explains what a kilowatt hour is.

We all know that c are rated in watts, such as a 60 watt light bulb or a 100 watt light bulb. How much you pay for using a light bulb on depends on how long you leave it on for and the wattage rating of the light bulb.

Most power calculation is based on hours. If you turned a 100 Watt light bulb on for 1 hour, then you have used 100 Watt hours. Likewise if you turn the same light bulb on for 2 hours, then you have used 200 Watt hours. Notice that we simply multiply the watts of the light bulb by the number of hours it is left on.

Watt Hours = Watts Used * Hours Used

Item used

Time used for

Watt hours Used

100 watt light bulb

1 hour

100

100 watt light bulb

5 hours

500

100 watt light bulb

24 hours

2,400

100 watt light bulb

24 hours a day for 30 days

72,000

The values in the last column get big fast when you start talking about how much power is used in a month. That is why most power use is measured in kilowatt hours. This simply means "1,000's of Watt hours". Using kilowatt hours, the above table becomes this.

kilowatt Hours Used = (Watts Used * Hours Used) / 1000

Item used

Time used for

kilowatt hours Used

100 watt light bulb

1 hour

0.1

100 watt light bulb

5 hours

0.5

100 watt light bulb

24 hours

2.4

100 watt light bulb

24 hours a day for 30 days

72

This last equation is the one that you should remember when doing kilowatt hour calculations.